Comparison and assessment of blood gas related quantities including base excess, the gas exchange indices, and temperature corrected pH/PO2/PCO2, as defined in approved NCCLS standard C12-A, using a computer simulation of input variables.

Blood gases and related quantities reported to clinicians have, since the earliest days, included both directly measured as well as calculated or estimated quantities. Some developed as substitutes for quantities that were or are difficult to measure routinely, others to explain relationships between older, difficult to measure quantities and newly measureable quantities, and still others attempt to better understand the physiology of the acid-base process. The net result is a plethora of acid-base and related quantities that may be reported by different blood gas systems. In an attempt to address the issue of which quantities have stood the test of usefulness over time, and further, to examine the optimum algorithm for use in quantification, the NCCLS has developed, through its consensus process, a recommended set of quantities and their quantifying algorithms. We have studied these quantities and compared them with some other recognized approaches and present our analysis in this report. The major conclusion is that among those quantities recommended, the NCCLS algorithms present the most sensible overall approach and that we would recommend their use as described so that the quantities can be most effectively applied clinically, without differences in final values occurring due solely simple algorithm differences.

Biosafety implications in sample introduction: module design characteristics for discrete-sample systems used in critical whole blood analyte testing environments.

Systems designed for the measurement of pH/blood gases and expanded versions of these systems that include the ability to measure electrolytes or other related quantities, all incorporate one or more sampling modules that are limited in their ability to allow for the safe handling of potentially biohazardous blood samples. Systems that provide for injection of sample from a syringe use more than the required volume for sample testing and have the potential for causing splash-back of the sample if the introduction port is blocked. The probes of aspiration-based systems require manual dexterity by the operator and present the possibility of operator injury with a contaminated probe tip or the possibility of system damage as the probe extends and the operator moves the collection device into place. Some systems have the potential for both types of biohazards. This report describes the implications for system design of the sample collection devices commonly in use, and it offers a design solution that combines the ergonomics of an injection system and the operational advantages of an aspiration system, in combination, addressing the biosafety aspects in a unique fashion.